xcode->performance tool->allocation

i have started a new opengl project and builded in simulator.
then i ran xcode->performance tool->allocation.
i wanted to know how many MB are allocated when the app is running.
something i don't understand:
why in overall allocation the MB always grow?
(grow grow grow, without stopping!)

however, for a game in iphone 3 i have 12MB of memory before crash isn't it?
so do i have to reduce overall memory (column in performance tool->allocation) under this limit?
i have seen games with 40MB of overall memory with performance tool, and they doesn't crash...am i looking in a wrong column?